Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Reduced phloem uptake of Myzus persicae on an aphid resistant pepper accession
Sun, Mengjing ; Voorrips, Roeland E. ; Steenhuis-Broers, Greet ; van't Westende, Wendy ; Vosman, Ben - \ 2018
BMC Plant Biology 18 (2018)1. - ISSN 1471-2229
Aphid resistance screening - Callose - Capsicum baccatum - EPG - Real-time PCR

Background: The green peach aphid (GPA), Myzus persicae, is economically one of the most threatening pests in pepper cultivation, which not only causes direct damage but also transmits many viruses. Breeding aphid resistant pepper varieties is a promising and environmentally friendly method to control aphid populations in the field and in the greenhouse. Until now, no strong sources of resistance against the GPA have been identified. Therefore the main aims of this study were to identify pepper materials with a good level of resistance to GPA and to elucidate possible resistance mechanisms. Results: We screened 74 pepper accessions from different geographical areas for resistance to M. persicae. After four rounds of evaluation we identified one Capsicum baccatum accession (PB2013071) as highly resistant to M. persicae, while the accessions PB2013062 and PB2012022 showed intermediate resistance. The resistance of PB2013071 resulted in a severely reduced uptake of phloem compared to the susceptible accession, as determined by Electrical Penetration Graph (EPG) studies. Feeding of M. persicae induced the expression of callose synthase genes and resulted in callose deposition in the sieve elements in resistant, but not in susceptible plants. Conclusions: Three aphid resistant pepper accessions were identified, which will be important for breeding aphid resistant pepper varieties in the future. The most resistant accession PB2013071 showed phloem-based resistance against aphid infestation.

Perennial Grass Bioenergy Cropping on Wet Marginal Land : Impacts on Soil Properties, Soil Organic Carbon, and Biomass During Initial Establishment
Das, Srabani ; Teuffer, Karin ; Stoof, Cathelijne R. ; Walter, Michael F. ; Walter, M.T. ; Steenhuis, Tammo S. ; Richards, Brian K. - \ 2018
Bio Energy Research 11 (2018)2. - ISSN 1939-1234 - p. 262 - 276.
Active carbon - Marginal soil - Reed canarygrass - Soil organic carbon - Switchgrass - Wet aggregate stability
The control of soil moisture, vegetation type, and prior land use on soil health parameters of perennial grass cropping systems on marginal lands is not well known. A fallow wetness-prone marginal site in New York (USA) was converted to perennial grass bioenergy feedstock production. Quadruplicate treatments were fallow control, reed canarygrass (Phalaris arundinaceae L. Bellevue) with nitrogen (N) fertilizer (75 kg N ha−1), switchgrass (Panicum virgatum L. Shawnee), and switchgrass with N fertilizer (75 kg N ha−1). Based on periodic soil water measurements, permanent sampling locations were assigned to various wetness groups. Surface (0–15 cm) soil organic carbon (SOC), active carbon, wet aggregate stability, pH, total nitrogen (TN), root biomass, and harvested aboveground biomass were measured annually (2011–2014). Multi-year decreases in SOC, wet aggregate stability, and pH followed plowing in 2011. For all years, wettest soils had the greatest SOC and active carbon, while driest soils had the greatest wet aggregate stability and lowest pH. In 2014, wettest soils had significantly (p < 0.0001) greater SOC and TN than drier soils, and fallow soils had 14 to 20% greater SOC than soils of reed canarygrass + N, switchgrass, and switchgrass + N. Crop type and N fertilization did not result in significant differences in SOC, active carbon, or wet aggregate stability. Cumulative 3-year aboveground biomass yields of driest switchgrass + N soils (18.8 Mg ha−1) were 121% greater than the three wettest switchgrass (no N) treatments. Overall, soil moisture status must be accounted for when assessing soil dynamics during feedstock establishment.
Hotspots of nitrous oxide emission in fertilized and unfertilized perennial grasses
Mason, Cedric W. ; Stoof, Cathelijne R. ; Richards, Brian K. ; Das, Srabani ; Goodale, Christine L. ; Steenhuis, Tammo S. - \ 2017
Soil Science Society of America Journal 81 (2017)3. - ISSN 0361-5995 - p. 450 - 458.
Hotspots of nitrous oxide (N2O) emission are thought to contribute substantially to annual emissions from agricultural soils. We observed N2O fluxes from fertilized and unfertilized C3 and C4 perennial grasses on a wet silt loam soil in New York, United States during the growing season in 2013, 2014, and 2015 using static chambers. Analysis of N2O hotspots within the research plots revealed that hotspots contributed between 34.3 and 39.1% of the total emissions, and constituted between 0.8% and 5.0% of all flux observations. Hotspots were more frequent and of greater magnitude in the fertilized treatments, and occurred when soil temperature was greater than 9.1°C and soil moisture was between about 40% and 80% water filled pore space (WFPS). A single chamber location in the fertilized switchgrass treatment was consistently a hotspot for N2O emission, suggesting that hotspots maintain a stable spatial pattern over extended periods. The maximum magnitude of N2O hotspot emission exhibited a relationship to soil temperature that is similar to that of the microbial growth rate constant.
Characterization of degraded soils in the humid Ethiopian highlands
Tebebu, Tigist Y. ; Bayabil, Haimanote K. ; Stoof, C.R. ; Giri, Shree K. ; Gessess, A.A. ; Tilahun, Seifu A. ; Steenhuis, Tammo S. - \ 2017
Land Degradation and Development 28 (2017)7. - ISSN 1085-3278 - p. 1891 - 1901.
Hard pan is a major cause of land degradation that affects agricultural productivity in developing countries. However, relatively little is known about the interaction of land degradation and hardpans. The objective of this study was, therefore, to investigate soil degradation and the formation of hardpans in crop/livestock mixed rainfed agriculture systems and to assess how changes in soil properties are related to the conversion of land from forest to agriculture. Two watersheds (Anjeni and Debre Mewi) were selected in the humid Ethiopian highlands. For both watersheds, 0-45 cm soil penetration resistance (SPR, n = 180) and soil physical properties (particle size, SOM, pH, base ions, CEC, silica content, bulk density and moisture content) were determined at 15 cm depth increments for three land uses: cultivated, pasture and forest. SPR of agricultural fields was significantly greater than that of forest lands. Dense layers with a critical SPR threshold of ≥ 2000 kPa were observed in the cultivated and pasture lands starting at a depth of 15-30 cm but did not occur in the undisturbed forest land. Compared with the original forest soils, agricultural fields were: lower in organic matter, CEC, and exchangeable base cations; more acidic; had a higher bulk density and more fine particles (clay and silt); and contained less soluble silica. Overall, our findings suggest that soil physical and chemical properties in agricultural lands deteriorated, causing disintegration of soil aggregates resulting in greater sediment concentration in infiltration water that clogged up macro-pores, thereby disconnecting deep flow paths found in original forest soils.
Aphid resistance in a Capsicum collection
Voorrips, R.E. ; Steenhuis-Broers, M.M. ; Westende, W.P.C. van 't; Vosman, B. - \ 2016
In: 2016 Proceedings of the XVIth EUCARPIA Capsicum and Eggplant Working Group Meeting. - Budapest, Hungary : Eucarpia - ISBN 9786155270277
Nitrous Oxide and Methane Fluxes from Smallholder Farms: A Scoping Study in the Anjeni Watershed.
Bayabil, Haimanote K. ; Stoof, C.R. ; Mason, C. ; Richards, B.K. ; Steenhuis, T.S. - \ 2016
Climate 4 (2016)4. - ISSN 2225-1154
While agricultural practices are widely reported to contribute to anthropogenic greenhouse gas (GHG) emissions, there are only limited measurements available for emission rates in the monsoon climate of the African continent. We conducted a scoping study to measure nitrous oxide (N2O-N) and methane (CH4) emission rates from 24 plots constructed on smallholder agricultural farms along the slope catena of three transects in the sub-humid Anjeni watershed in the Ethiopian highlands. Greenhouse gas flux samples were collected in 2013, before, towards the end, and after the rainy monsoon phase. At each location, three plots were installed in groups: two plots grown with barley (one enriched with charcoal and the other without soil amendment) and lupine was grown on the third plot without any soil amendment. Preliminary study results showed that nitrous oxide emission rates varied from −275 to 522 μg·m−2·h−1 and methane emissions ranged from −206 to 264 μg·m−2·h−1 with overall means of 51 and 5 μg·m−2·h−1 for N2O-N and CH4, respectively. Compared with the control, charcoal and lupine plots had elevated nitrous oxide emissions. Plots amended with charcoal showed on average greater methane uptake than was emitted. While this study provides insights regarding nitrous oxide and methane emission levels from smallholder farms, studies of longer durations are needed to verify the results
Morphological dynamics of gully systems in the subhumid Ethiopian Highlands : the Debre Mawi watershed
Zegeye, Assefa D. ; Langendoen, Eddy J. ; Stoof, C.R. ; Tilahun, Seifu A. ; Dagnew, Dessalegn C. ; Zimale, Fasikaw A. ; Guzman, C.D. ; Yitaferu, B. ; Steenhuis, T.S. - \ 2016
Soil 2 (2016). - ISSN 2199-3971 - p. 443 - 458.
Gully expansion in the Ethiopian Highlands dissects vital agricultural lands with the eroded materials adversely impacting downstream resources, for example as they accumulate in reservoirs. While gully expansion and rehabilitation have been more extensively researched in the semiarid region of Ethiopia, few studies have been conducted in the (sub)humid region. For that reason, we assessed the severity of gully erosion by measuring the expansion of 13 selected permanent gullies in the subhumid Debre Mawi watershed, 30 km south of Lake Tana, Ethiopia. In addition, the rate of expansion of the entire drainage network in the watershed was determined using 0.5 m resolution aerial imagery from flights in 2005 and 2013. About 0.6 Mt (or 127 t ha−1 yr−1) of soil was lost during this period due to actively expanding gullies. The net gully area in the entire watershed increased more than 4-fold from 4.5 ha in 2005 to 20.4 ha in 2013 (> 3 % of the watershed area), indicating the growing severity of gully erosion and hence land degradation in the watershed. Soil losses were caused by upslope migrating gully heads through a combination of gully head collapse and removal of the failed material by runoff. Collapse of gully banks and retreat of headcuts was most severe in locations where elevated groundwater tables saturated gully heads and banks, destabilizing the soils by decreasing the shear strength. Elevated groundwater tables were therefore the most important cause of gully expansion. Additional factors that strongly relate to bank collapse were the height of the gully head and the size of the drainage area. Soil physical properties (e.g., texture and bulk density) only had minor effects. Conservation practices that address factors controlling erosion are the most effective in protecting gully expansion. These consist of lowering water table and regrading the gully head and sidewalls to reduce the occurrence of gravity-induced mass failures. Planting suitable vegetation on the regraded gully slopes will in addition decrease the risk of bank failure by reducing pore-water pressures and reinforcing the soil. Finally, best management practices that decrease runoff from the catchment will reduce the amount of gully-related sediment loss.
Antibiosis resistance against larval cabbage root fly, Delia radicum, in wild Brassica-species
Wang, Shuhang ; Voorrips, Roeland E. ; Steenhuis-Broers, Greet ; Vosman, Ben ; Loon, Joop J.A. van - \ 2016
Euphytica (2016). - ISSN 0014-2336 - 17 p.
Brassica oleracea - Cabbage root maggot - Eclosion - Host plant resistance - Insect resistance

Cabbage root flies (Delia radicum) are a major threat to cabbage production in Western Europe and North America. Host plant resistance is the most promising option in controlling cabbage root fly damage. In a no-choice field test, we evaluated 94 accessions belonging to 16 Brassica-species for antibiosis resistance against the larvae. Thirteen accessions were selected as putatively resistant, which were subsequently re-tested in the greenhouse. The proportion of eclosed flies was introduced as the main parameter to assess antibiosis in the greenhouse, together with other insect and plant parameters. High levels of antibiosis resistance were identified in B. fruticulosa PI663081 and B. spinescens BRA2994, with significantly lower proportions of eclosed flies (1 % of the number of eggs used for infestation) compared to other accessions. Both species are difficult to cross with B. oleracea. Plants with a high level of antibiosis and medium to high tolerance were found in several accessions of other Brassica species (B. villosa BRA2922, B. montana BRA2950, B. hilarionis HRIGU12483, B. macrocarpa BRA2944) which are more amenable for crossing with B. oleracea. Selection of the most resistant plants belonging to these accessions may yield promising candidates for breeding cabbages resistant to Delia radicum.

Can pore-clogging by ash explain post-fire runoff?
Stoof, Cathelijne R. ; Gevaert, Anouk I. ; Baver, Christine ; Hassanpour, Bahareh ; Morales, Verónica L. ; Zhang, Wei ; Martin, Deborah ; Giri, Shree K. ; Steenhuis, Tammo S. - \ 2016
International Journal of Wildland Fire 25 (2016)3. - ISSN 1049-8001 - p. 294 - 305.
hydraulic conductivity - infiltration - wildland fire ash

Ash plays an important role in controlling runoff and erosion processes after wildfire and has frequently been hypothesised to clog soil pores and reduce infiltration. Yet evidence for clogging is incomplete, as research has focussed on identifying the presence of ash in soil; the actual flow processes remain unknown. We conducted laboratory infiltration experiments coupled with microscope observations in pure sands, saturated hydraulic conductivity analysis, and interaction energy calculations, to test whether ash can clog pores (i.e. block pores such that infiltration is hampered and ponding occurs). Although results confirmed previous observations of ash washing into pores, clogging was not observed in the pure sands tested, nor were conditions found for which this does occur. Clogging by means of strong attachment of ash to sand was deemed unlikely given the negative surface charge of the two materials. Ponding due to washing in of ash was also considered improbable given the high saturated conductivity of pure ash and ash-sand mixtures. This first mechanistic step towards analysing ash transport and attachment processes in field soils therefore suggests that pore clogging by ash is unlikely to occur in sands. Discussion is provided on other mechanisms by which ash can affect post-fire hydrology. Journal compilation

Effects of a deep-rooted crop and soil amended with charcoal on spatial and temporal runoff patterns in a degrading tropical highland watershed
Bayabil, Haimanote K. ; Tebebu, Tigist Y. ; Stoof, Cathelijne R. ; Steenhuis, Tammo S. - \ 2016
Hydrology and Earth System Sciences 20 (2016). - ISSN 1027-5606 - p. 875 - 885.

Placement and hence performance of many soil and water conservation structures in tropical highlands has proven to be challenging due to uncertainty of the actual location of runoff-generating areas in the landscape. This is the case especially in the (sub-)humid areas of the Ethiopian highlands, resulting in limited success of such conservation measures. To improve understanding of the effect of land use on spatial and temporal runoff patterns in the Ethiopian highlands, we monitored runoff volumes from 24 runoff plots constructed in the 113 ha Anjeni watershed, where historical data of rainfall and stream discharge were available. In addition, we assessed the effectiveness of charcoal amendment of the soil and crop rooting depth in reducing runoff, and we compared the effect of lupine (a deep-rooted crop) to that of barley. We also measured daily rainfall, surface runoff, and root zone moisture contents during the monsoon seasons of 2012 and 2013 (with all plots being tilled in 2012, but only barley plots tilled in 2013). In addition, we analyzed long-term surface runoff from four plots, and outlet discharge data from the research site (1989-1993) were analyzed and compared with our observations. Results showed that the degrees of soil degradation and soil disturbance (tillage) were significant factors affecting plot-scale runoff responses. As expected, runoff was greater from more degraded soils. Overall, under the commonly applied lupine cropping practice, runoff was higher than under the commonly applied barley cropping practice. In particular, considerable difference was observed during smaller rainfall events (approximately <20 mm) in 2013, when lupine plots (non-tilled) had greater runoff than barley plots (tilled). Charcoal tended to decrease runoff, but results were not significant.

Spring-Thaw Nitrous Oxide Emissions from Reed Canarygrass on Wetness-Prone Marginal Soil in New York State
Mason, C. ; Stoof, C.R. ; Richards, B.K. ; Rossiter, D. ; Steenhuis, T.S. - \ 2016
Soil Science Society of America Journal 80 (2016)2. - ISSN 0361-5995 - p. 428 - 437.
In temperate climates, a significant fraction of annual emissions of nitrous oxide (N2O) from agricultural land can occur during soil thaw in late winter and early spring. The objective of this study is to determine the impact of land use change from long-term fallow grassland to managed perennial grass crops on these thaw-related N2O emissions, and to identify field-scale drivers that influence emissions. Using static chambers, we monitored mid-afternoon N2O fluxes during the 2013 spring thaw from March 27 to April 7, observing fallow grassland and second year reed canarygrass (Phalaris arundinaceae L., v. Bellevue) over a short topographical gradient. Soil temperature, soil moisture and residual above-ground biomass were also observed, as were
hourly air temperature and precipitation. Fluxes of N2O were generally low (-9.8 to 21.3 μg N2O-N m-2 hr-1) except for one observation of 77.6 μg N2O-N m-2 hr-1. Hot-moment analysis, non-parametric statistical tests, and ANOVA results showed that downslope positions converted to managed and fertilized grass had significantly higher N2O emissions compared to the fallow and upslope positions. We found that these downslope managed grass sites had mean soil
moisture of 75.0 % water filled pore space (WFPS) and less insulating residual above-ground biomass than the fallow grassland. Our results suggest that converting fallow grassland to managed perennial grass cropping systems for bioenergy or other uses could increase springthaw N2O emissions in wetness-prone areas.
Untapped Potential : Opportunities and Challenges for Sustainable Bioenergy Production from Marginal Lands in the Northeast USA
Stoof, C.R. ; Richards, B.K. ; Woodbury, P.B. ; Fabio, E.S. ; Brumbach, A.R. ; Cherney, Jerry ; Das, Srabani ; Geohring, Larry ; Hansen, Julie ; Hornesky, Josh ; Mayton, Hilary ; Mason, Cedric ; Ruestow, Gerry ; Smart, L.B. ; Volk, T.A. ; Steenhuis, T.S. - \ 2015
Bio Energy Research 8 (2015)2. - ISSN 1939-1234 - p. 482 - 501.
Impacts - Marginal land - Northeast USA - Perennial grass - Policy - Production - Second-generation bioenergy feedstocks - Short-rotation woody crops

Over two million hectares of marginal land in the Northeast USA no longer used for agriculture may be suitable and available for production of second-generation cellulosic bioenergy crops, offering the potential for increased regional bioenergy production without competing with food production on prime farmland. Current yields of perennial bioenergy grasses and short-rotation woody crops range from 2.3 to 17.4 and 4.5 to 15.5 Mg/ha, respectively, and there is great potential for increased yields. Regional advantages for bioenergy development include abundant water resources, close proximity between production and markets, and compatibility of bioenergy cropping systems with existing agriculture. As New York and New England (a subset of the Northeast region) account for ~85 % of the nation’s heating oil consumption, production of bioheat, biopower, and combined heat and power could substantially reduce the region’s dependence on imported petroleum. While numerous grassroots efforts are underway in the region across supply chains, bioenergy development faces several challenges and unknowns in terms of environmental impact, production, yields, socioeconomics, and policy. We explore the opportunities for second-generation bioenergy production on the unused marginal lands of the Northeast USA and discuss the challenges to be addressed to promote sustainable bioenergy production on the region’s underutilized marginal land base.

Park design between community and professionals : The Wollefoppenpark in Rotterdam
Brinkhuijsen, Marlies ; Steenhuis, Marinke - \ 2015
Jola : Journal of Landscape Architecture 10 (2015)3. - ISSN 1862-6033 - p. 28 - 37.

The Zevenkamp district in eastern Rotterdam conceals a specimen of Dutch landscape architecture from the early 1980s - the Wollefoppenpark and Noordelijk Wijkpark, a structure of green spaces connecting the district with the open polder landscape. The park was designed as a robust framework that would last, with patches that could change over time according to use and preferences. Thirty-five years later, with the park now fully grown, community initiatives have transformed a crucial part of it. We scrutinize the flexibility and versatility of the design over time and with regard to stability of the framework, intended adaptability of patches, multifunctionality, and new appropriation. We conclude that, for the most part, the framework is indeed as strong as it was intended to be and that the patches proved flexible but, at the same time, community initiatives challenge the quality of public space. The latter case indicates the necessity to strategically rethink the relation between community initiatives and professional design (Fig. 1).

QTL mapping of thrips resistance in pepper
Maharijaya, A. ; Vosman, B.J. ; Steenhuis-Broers, M.M. ; Pelgrom, K.T.B. ; Purwito, A. ; Visser, R.G.F. ; Voorrips, R.E. - \ 2015
Theoretical and Applied Genetics 128 (2015)10. - ISSN 0040-5752 - p. 1945 - 1956.
Thrips is one of the most damaging pests in pepper (Capsicum). Resistance to thrips was identified in Capsicum annuum. This study was aimed at the elucidation of the genetic background of thrips resistance in Capsicum through QTL mapping. The QTL analysis was carried out for Frankliniella occidentalis resistance in an F2 population consisting of 196 plants derived from an interspecific cross between the highly resistant C. annuum AC 1979 as female parent and the highly susceptible C. chinense 4661 as male parent. Fifty-seven SSR, 109 AFLP, and 5 SNP markers were used to construct a genetic map with a total length of 1636 cM. Damage caused by larvae and the survival of first and second instar larval stages observed in a no-choice test were used as parameters of resistance. Interval mapping detected one QTL for each of these parameters, all co-localizing near the same marker on chromosome 6. Use of this marker as co-factor in a multiple-QTL mapping analysis failed to uncover any additional QTLs. This QTL explained about 50 % of the genetic variation, and the resistance allele of this QTL was inherited from the resistant parent. Thrips resistance was not linked to trichome density.
Assessing the potential of biochar and charcoal to improve soil hydraulic properties in the humid Ethiopian Highlands: The Anjeni watershed
Bayabil, H.K. ; Stoof, C.R. ; Lehmann, J.C. ; Yitaferu, B. ; Steenhuis, T.S. - \ 2015
Geoderma 243-244 (2015). - ISSN 0016-7061 - p. 115 - 123.
central rift-valley - organic-matter - physical-properties - land management - nile basin - agronomic performance - chemical-properties - climate-change - maize yield - retention
Biochar has shown promise for restoring soil hydraulic properties. However, biochar production could be expensive in the developing world, while charcoal iswidely available and cheap. The objective of this study is therefore to investigate whether some of the charcoal made in developing countries can also be beneficial for improving soil hydraulic properties, and explore whether charcoal could potentially restore the degraded African soils. Laboratory and field experiments were conducted in the Anjeni watershed in the Ethiopian highlands, to measure soil physical properties including soil moisture retention and infiltration rates. Soils were dominantly clayey with pH in the acidic range, low organic carbon content, and steady infiltration rates ranging between 2 and 36 mm/h. Incorporation of woody feedstock (Acacia, Croton, and Eucalyptus) charcoals significantly decreased moisture retention at lower tensions (10 and 30 kPa), resulting in an increase in relative hydraulic conductivity coefficients at these tensions. While wood (oak) biochar decreased moisture retention at low tensions, corn biochar increased retention, but effects were only slight and not significant. Surprisingly, available water content was not significantly affected by any of the amendments. Overall findings suggest that wood charcoal amendments can improve soil hydraulic properties of degraded soils, thereby potentially reducing runoff and erosion.
The home food environment of overweight gatekeepers in the Netherlands
Poelman, M.P. ; Vet, E. de; Velema, E. ; Seidell, J.C. ; Steenhuis, I.H.M. - \ 2015
Public Health Nutrition 18 (2015)10. - ISSN 1368-9800 - p. 1815 - 1823.
randomized controlled-trial - eating behaviors - portion sizes - weight-loss - consumption volume - vegetable intake - plate-size - obesity - illusions - fruit
Objective: The aim of the present study was to gain insight into (i) processed snackfood availability, (ii) processed snack-food salience and (iii) the size of dinnerware among households with overweight gatekeepers. Moreover, associations between gatekeepers’ characteristics and in-home observations were determined. Design: A cross-sectional observation of home food environments was conducted as part of a baseline measurement of a larger study. Setting: Home food environments of overweight and obese gatekeepers in the Netherlands. Subjects: Household gatekeepers (n 278). Mean household size of the gatekeepers was 3·0 (SD 1·3) persons. Mean age of the gatekeepers was 45·7 (SD 9·2) years, 34·9 % were overweight and 65·1 % were obese. Of the gatekeepers, 20·9 % had a low level of education and 42·7 % had a high level of education. Results: In 70 % of the households, eight or more packages of processed snack foods were present. In 54 % of the households, processed snack foods were stored close to non-processed food items and in 78 % of households close to non-food items. In 33 % of the households, processed snack foods were visible in the kitchen and in 15 % of the households processed snack foods were visible in the living room. Of the dinnerware items, 14 % (plates), 57 % (glasses), 78 % (dessert bowls), 67 % (soup bowls) and 58 % (mugs) were larger than the reference norms of the Netherlands Nutrition Centre Foundation. Older gatekeepers used significantly smaller dinnerware than younger gatekeepers. Conclusions: Environmental factors endorsing overconsumption are commonly present in the home environments of overweight people and could lead to unplanned eating or passive overconsumption.
PortionControl@HOME: Results of a Randomized Controlled Trial Evaluating the Effect of a Multi-Component Portion Size Intervention on Portion Control Behavior and Body Mass Index
Poelman, M.P. ; Vet, E. de; Velema, E. ; Boer, M.R. de; Seidell, J.C. ; Steenhuis, I.H.M. - \ 2015
Annals of behavioral medicine 49 (2015)1. - ISSN 0883-6612 - p. 18 - 28.
energy-intake - food-intake - consumption volume - relapse prevention - obesity epidemic - college-students - young-adults - impact - maintenance - consumers
Background Food portion sizes influence energy intake. Purpose The purpose of this paper is to determine effectiveness of the “PortionControl@HOME” intervention on body mass index and portion control behavior. Methods A randomized controlled trial among 278 overweight and obese participants was conducted. PortionControl@HOME aimed to increase: portion size awareness, portion control behavior, portion control cooking skills, and to create a home environment favoring portion control. Results Intention-to-treat multi-level regression analysis indicated statistically significant effects of the intervention on portion control behavior at 3, 6, and 12 months follow-up. The effect on body mass index was significant only at 3 months follow-up and when outliers (n¿=¿3) were excluded (B¿=¿-0.45; 95 %CI¿=¿-0.88 to -0.04). The intervention effect on body mass index was mediated by portion control behavior. Conclusions The intervention improves portion control behavior, which in turn influence body mass index. Once the intervention ceased, sustained effects on body mass index were no longer evident. (Current-Controlled-Trials ISRCTN12363482).
Capillary pressure overshoot for unstable wetting fronts is explained by Hoffman's velocity-dependent contact-angle relationship
Baver, Christine ; Parlange, J.Y. ; Stoof, C.R. ; DiCarlo, D.A. ; Wallach, Rony ; Durnford, Deanna S. ; Steenhuis, Tammo S. - \ 2014
Water Resources Research 50 (2014)6. - ISSN 0043-1397 - p. 5290 - 5297.
Pore velocity-dependent dynamic contact angles provide a mechanism for explaining the formation of fingers/columns in porous media. To study those dynamic contact angles when gravity is present, rectangular capillary tubes were used to facilitate observation of the complete interface without geometric distortion. Results show that the Hoffman (1975) relationship between dynamic contact angle and water velocity applies to gravity-affected flow fields, and that it (when adjusted for nonzero static contact angles) can be used to model dynamic capillary pressures for unstable wettings fronts in porous media by assuming that (1) pressure at the wetting front is discontinuous, (2) the flow field behind the fingertip is highly heterogeneous, and (3) the front line advances one or a few pores at the time. We demonstrate the utility of the Hoffman relationship for porous media with a published infiltration experiment by calculating the capillary pressure successfully at the unstable wetting front as a function of the flux of water in the finger and the grain size diameter.
Effect of Hydrofracking Fluid on Colloid Transport in the Unsaturated Zone
Sang, Wenjing ; Stoof, C.R. ; Zhang, W. ; Morales, Verónica L. ; Gao, Bin ; Kay, Robert W. ; Lin, L. ; Zhang, Yalei ; Steenhuis, Tammo S. - \ 2014
Environmental Science and Technology 48 (2014)14. - ISSN 0013-936X - p. 8266 - 8274.
Hydraulic fracturing is expanding rapidly in the US to meet increasing energy demand and requires high volumes of hydrofracking fluid to displace natural gas from shale. Accidental spills and deliberate land application of hydrofracking fluids, which return to the surface during hydrofracking, are common causes of environmental contamination. Since the chemistry of hydrofracking fluids favors transport of colloids and mineral particles through rock cracks, it may also facilitate transport of in situ colloids and associated pollutants in unsaturated soils. We investigated this by subsequently injecting deionized water and flowback fluid at increasing flow rates into unsaturated sand columns containing colloids. Colloid retention and mobilization was measured in the column effluent and visualized in situ with bright field microscopy. While <5% of initial colloids were released by flushing with deionized water, 32–36% were released by flushing with flowback fluid in two distinct breakthrough peaks. These peaks resulted from 1) surface tension reduction and steric repulsion and 2) slow kinetic disaggregation of colloid flocs. Increasing the flow rate of the flowback fluid mobilized an additional 36% of colloids, due to the expansion of water filled pore space. This study suggests that hydrofracking fluid may also indirectly contaminate groundwater by remobilizing existing colloidal pollutants.
Portion Control: Dealing with the supersized food environment
Poelman, M.P. - \ 2014
University; Vrije Universiteit. Promotor(en): I.H.M. Steenhuis; J.C. Seidell, co-promotor(en): Emely de Vet. - Amsterdam : VU University - ISBN 9789461087942 - 202
voeding en gezondheid - portiegrootte - overgewicht - obesitas - voedselconsumptie - gewichtsverliezen - nutrition and health - portion size - overweight - obesity - food consumption - weight losses
In dit proefschrift wordt de voedselomgeving met betrekking tot portiegrootte verkend en wordt er een uitgebreide gewichtsmanagement-interventie gericht op portiecontrole ontwikkeld en geëvalueerd.
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